The factor, and a shortcut
One kilogram is 35.274 avoirdupois ounces, so to get kilograms you divide the ounces by 35.274. For a quick head estimate, divide by 35: 100 oz is roughly 2.86 kg, and dividing by 35 gives 2.86 — close enough for everyday use.
Common conversions
| Ounces | Grams | Kilograms |
|---|---|---|
| 1 oz | 28.35 g | 0.028 kg |
| 4 oz | 113.4 g | 0.113 kg |
| 8 oz | 226.8 g | 0.227 kg |
| 16 oz (1 lb) | 453.6 g | 0.454 kg |
| 32 oz | 907.2 g | 0.907 kg |
| 100 oz | 2,835 g | 2.835 kg |
Sixteen ounces is one pound, which is 0.4536 kg — the number behind the "a pound is about half a kilo" rule of thumb.
The gotcha: avoirdupois vs troy ounces
"Ounce" means two different weights depending on what you are weighing. Food, mail and consumer goods use the avoirdupois ounce (28.35 g). Gold, silver and platinum are always sold by the troy ounce (31.10 g), which is about 10 percent heavier.
Weighing a gold bar with the food ounce would overstate its count by about 10 percent — a costly slip.
Two points worth remembering
- The exact factor. One avoirdupois ounce is defined as exactly 28.349523125 g, from the pound (0.45359237 kg) split into 16. Rounding to 28.35 is fine unless you are baking or in a lab.
- Mass, not weight. Both units measure mass and match anywhere, so this conversion is the same on Earth or the Moon.
Common questions
How many ounces are in a kilogram?
A kilogram is 35.274 ounces (avoirdupois). Going the other way, one ounce is 0.02835 kg, or 28.35 grams.
How do I convert ounces to kilograms?
Multiply the ounces by 0.02835, or divide by 35.274. For example, 16 oz (one pound) is 0.4536 kg.
Is a troy ounce the same as a regular ounce?
No. A troy ounce is 31.10 grams and is used only for gold, silver and platinum. The everyday ounce for food and shipping is the avoirdupois ounce at 28.35 grams, about 10 percent lighter.
